######################## BEGIN LICENSE BLOCK ########################
# The Original Code is mozilla.org code.
#
# The Initial Developer of the Original Code is
# Netscape Communications Corporation.
# Portions created by the Initial Developer are Copyright (C) 1998
# the Initial Developer. All Rights Reserved.
#
# Contributor(s):
#   Hui (zhengzhengzheng@gmail.com) - port to Ruby
#   Mark Pilgrim - first port to Python
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
# 
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
# 
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
# 02110-1301  USA
######################### END LICENSE BLOCK #########################

require 'UniversalDetector'
require 'CharSetProber'

module Enumerable
    def reduceBlock(res)
        each { |n| res = yield(res, n) }
        res
    end
end

module UniversalDetector
    FREQ_CAT_NUM = 4

    UDF = 0 # undefined
    OTH = 1 # other
    ASC = 2 # ascii capital letter
    ASS = 3 # ascii small letter
    ACV = 4 # accent capital vowel
    ACO = 5 # accent capital other
    ASV = 6 # accent small vowel
    ASO = 7 # accent small other
    CLASS_NUM = 8 # total classes

    Latin1_CharToClass = [ \
      OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   # 00 - 07
      OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   # 08 - 0F
      OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   # 10 - 17
      OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   # 18 - 1F
      OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   # 20 - 27
      OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   # 28 - 2F
      OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   # 30 - 37
      OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   # 38 - 3F
      OTH, ASC, ASC, ASC, ASC, ASC, ASC, ASC,   # 40 - 47
      ASC, ASC, ASC, ASC, ASC, ASC, ASC, ASC,   # 48 - 4F
      ASC, ASC, ASC, ASC, ASC, ASC, ASC, ASC,   # 50 - 57
      ASC, ASC, ASC, OTH, OTH, OTH, OTH, OTH,   # 58 - 5F
      OTH, ASS, ASS, ASS, ASS, ASS, ASS, ASS,   # 60 - 67
      ASS, ASS, ASS, ASS, ASS, ASS, ASS, ASS,   # 68 - 6F
      ASS, ASS, ASS, ASS, ASS, ASS, ASS, ASS,   # 70 - 77
      ASS, ASS, ASS, OTH, OTH, OTH, OTH, OTH,   # 78 - 7F
      OTH, UDF, OTH, ASO, OTH, OTH, OTH, OTH,   # 80 - 87
      OTH, OTH, ACO, OTH, ACO, UDF, ACO, UDF,   # 88 - 8F
      UDF, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   # 90 - 97
      OTH, OTH, ASO, OTH, ASO, UDF, ASO, ACO,   # 98 - 9F
      OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   # A0 - A7
      OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   # A8 - AF
      OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   # B0 - B7
      OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   # B8 - BF
      ACV, ACV, ACV, ACV, ACV, ACV, ACO, ACO,   # C0 - C7
      ACV, ACV, ACV, ACV, ACV, ACV, ACV, ACV,   # C8 - CF
      ACO, ACO, ACV, ACV, ACV, ACV, ACV, OTH,   # D0 - D7
      ACV, ACV, ACV, ACV, ACV, ACO, ACO, ACO,   # D8 - DF
      ASV, ASV, ASV, ASV, ASV, ASV, ASO, ASO,   # E0 - E7
      ASV, ASV, ASV, ASV, ASV, ASV, ASV, ASV,   # E8 - EF
      ASO, ASO, ASV, ASV, ASV, ASV, ASV, OTH,   # F0 - F7
      ASV, ASV, ASV, ASV, ASV, ASO, ASO, ASO,   # F8 - FF
    ]

    # 0 : illegal 
    # 1 : very unlikely 
    # 2 : normal 
    # 3 : very likely
    Latin1ClassModel = [ \
    # UDF OTH ASC ASS ACV ACO ASV ASO
       0,  0,  0,  0,  0,  0,  0,  0,  # UDF
       0,  3,  3,  3,  3,  3,  3,  3,  # OTH
       0,  3,  3,  3,  3,  3,  3,  3,  # ASC
       0,  3,  3,  3,  1,  1,  3,  3,  # ASS
       0,  3,  3,  3,  1,  2,  1,  2,  # ACV
       0,  3,  3,  3,  3,  3,  3,  3,  # ACO
       0,  3,  1,  3,  1,  1,  1,  3,  # ASV
       0,  3,  1,  3,  1,  1,  3,  3,  # ASO
    ]

    class Latin1Prober < CharSetProber
        def initialize
            super
            reset()
        end

        def reset
            @_mLastCharClass = OTH
            @_mFreqCounter = [0] * FREQ_CAT_NUM
            super
        end

        def get_charset_name
            return "windows-1252"
        end

        def feed(aBuf)
            aBuf = filter_with_english_letters(aBuf)
            aBuf.each_char do |c|
                charClass = Latin1_CharToClass[c.get_byte(0)]
                freq = Latin1ClassModel[(@_mLastCharClass * CLASS_NUM) + charClass]
                if freq == 0
                    @_mState = :NotMe
                    break
                end
                @_mFreqCounter[freq] += 1
                @_mLastCharClass = charClass
            end        

            return get_state()
        end

        def get_confidence()
            if get_state() == :NotMe
                return 0.01
            end

            total = @_mFreqCounter.reduce(0, :+)
            if total < 0.01
                confidence = 0.0
            else
                confidence = (@_mFreqCounter[3] / total) - (@_mFreqCounter[1] * 20.0 / total)
            end
            if confidence < 0.0
                confidence = 0.0
            end
            # lower the confidence of latin1 so that other more accurate detector 
            # can take priority.
            confidence = confidence * 0.5
            return confidence
        end
    end
end
